Researchers Derive Safer Ways To Quantum Encrypt Data

A team of researchers from the University of Toronto led by Professor Hoi-Kwong Lo has devised a new quantum encryption method that is supposed to be a hard nut to crack even for the most sophisticated hackers. The discovery has made an appearance in the latest issue of Physical Review Letters.

Quantum Encryption, in theory, is as secure as it gets. It relies on the fact that any attempt by an eavesdropper to acquire encoded communication data will immediately lead to disturbances. The points of disturbances can be detected by valid users who hold a photon detector at each end. But photon detectors have been known to be vulnerable to side-channel attacks, most famously quantum hacking.

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The challenge for Professor Lo's team here was to fix the device problem and they have done so by a method called Measurement Device Independent QKD.  Measurement Device Independent QKD works between two users who send data signals to an untrusted relay, which may or may not be corrupted. The intermediate device then performs a joint measurement on the signals, which yields another point of comparison. Even if the device's detectors are arbitrarily flawed they wouldn't compromise security because the users at each end can themselves test the verity through the correlations in their own data.

So, even if a hacker tampers with the photon detectors and broadcast measurement results, they can be discarded by measuring against users' own data. This will help in noticing any subtle changes in the quantum data. A prototype is now under development and is expected to be ready within five years.

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